Forbidding Duemilanove / Mega to use USB power?

Hi,

my robot uses a Mega and a Duemilanove hooked up to the same power supply. Since a number of things (not least of all testing) depend on correct power-on order, I'd like to tell both of those Arduinos not to use USB power but external power exclusively. The Diecimila had a jumper to do that, but I need the memory of the Duemilanove and the pins of the Mega...

Thanks in advance, Björn

If you don't want them to use USB power then don't connect them to USB power. If you need it to run off of an external power source even when connected to the PC then you can modify a USB cable so that power isn't passed to the unit.

hello

Arduino switches the power from the usb to the external power connector automatically.

If the board is connected to an external power source you should be able to safely remove the usb cable.

the only issue might be the reset of the FTDI chip that might provoke a reset of the processor on the Arduino.

have you tried this?

m

Arduino switches the power from the usb to the external power connector automatically.

which kinda sucks if you need external power and the ability to program at the same time, the jumper was easy, the auto switch requires a modded cable or board

Well , on the other hand the jumper made life difficult for a lot of people.

anything that removes a jumper of a switch for me it's a good thing.

I'm actually very tempted to remove the reset switch as well but gianluca loves it a lot :)

m

That's kind of why I like the Seeeduino designed boards. They have user switches for power source (USB or external) and reset logic (DTR auto-reset on or off).

While that might give new comers too many choices to get wrong, it does allow experianced users to have the board operate as they wish for the application at hand.

Lefty

I didn't understand good if you have also a Diecimila, but in this cas you could swap the Atmega 168 and 328 chips of your Diecimila et Duemilanove, that would clear the problem on that side! ;)

Well , on the other hand the jumper made life difficult for a lot of people.

on yet another hand removing options is no proper way to deal with education

my bare bones board simply states it as a feature, do this if you want usb power do that if you want external

simple

If you never want them to use USB power then splice up a USB cable without the power in or cut the power trace from the USB socket...

Yeah the second is not too great if they are not going to be permenantly in the project but hey.

Forum Administrator

Hehe, did you give up your name?

Mowcius

The fact that there are many Arduino compatible boards out there is good.. Since no product will make everybody happy one can create his/her version of Arduino that would suit the 10/100/1000/etc people who share the same idea.

:)

PS I didn't give up my name but I'm not the only one administering the forum

massimo

I'm actually very tempted to remove the reset switch as well

I would cry without my reset button ;D!

I would cry without my reset button!

Don't cry, I know how you feel.

Mowcius

Don't cry, I know how you feel.

Perhaps there should be a support group for such things. I suppose we could include those of us who also miss the DTR jumper ;D!

I have never had to press the reset button on any of my Aduinos. What do you use it for?

I have never had to press the reset button on any of my Aduinos. What do you use it for?

As an easy example, consider a sketch that runs once and then “sleeps” by one mechanism or another. The reset button can be used to restart the sketch. Essentially the “fire” button on a TV-B-gone clone, but … provides “start/restart” functionality for an application where it doesn’t make sense to loop continuously.

I use the reset loads. It gets used for restarting sketches that have long waits or when I need to check that the setup code is working correctly or something. :)

Mowcius